DNA from ancient plague bacteria found in 1500 year-old teeth

In the middle of the 6th century, a devastating sickness swept across Asia, Europe, and northern Africa. The Plague of Justinian, as it was to be known, is believed to have killed between 25 and 50 million people across the world in just one year. Mortality rates in some cities were as high as 40%. Researchers recently confirmed that the Plague of Justinian was a pandemic outbreak of Bubonic Plague, but now the research has been taken one step further.

Using bacterial DNA extracted from 1500 year-old teeth of plague victims from Germany, scientists have reconstructed the genome of this deadly organism. This makes it the oldest pathogen genome ever recovered. The bacterial agent that causes plague is Yersinia pestis, a gram negative rod-shaped bacterium that is often carried by fleas. The Plague of Justinian is not the only time Y. pestis has taken a toll on humanity. Bubonic Plague was also the cause of the infamous Black Death during the 14th century.

By piecing together the genome of the Justinian strain of Y. pestis, researchers are able to compare it to the bacteria that caused plague in later centuries. The Justinian strain was found to have extremely high virulence similar to, but distinct from the later strains. That is, it was an evolutionary dead end for the bacteria. It was also confirmed that this pandemic originated in the far east, likely in what is modern day China.

Humanity is in a much better place when it comes to preventing bubonic plague thanks to improved sanitation and antibiotics. However, Y. pestis is still a deadly bacterium not to be taken lightly.